1. Field of the Invention
The present invention relates to a printer, and more particularly, to a device for cutting off a power supply of a printer.
2. Description of the Related Art
Users of output apparatuses such as laser beam printers (LBPs) can add desired functions to the output apparatuses other than functions basically provided to thereto. For example, a user can additionally mount expansion boards, a ROM board, or an interface board for use with a network. Also, a developer unit used in an output apparatus must be routinely replaced after a tower therein has been exhausted. In these cases, since a printer cover is opened when the board or the developer unit is mounted in the printer body, a current flowing through a circuit of the printer body must be cut off to protect the user.
When opening the printer cover of a conventional apparatus, the above operations are performed after separately cutting off a voltage (5V) of a laser scanning unit and a voltage (25V) required to drive a motor of the printer, or by cutting off a main power supply of the printer.
As described above, where a device for cutting off the power supply is not individually installed in the printer, or the power supply is cut off by respectively turning off multiple switches which are separately located in several positions of the printer when opening the printer cover, there is a problem in that the process for cutting off the power supply is complex and possibly unsafe.
To solve the above-described problems, various devices for cutting off the power supply of the printer have been proposed. FIG. 1 shows a basic configuration of one among the conventional devices for cutting off the power supply of the printer.
Referring to FIG. 1, a device for cutting off a power supply of a printer according to the related art includes a bracket 20 mounted on an upper frame 10 of the printer, an actuator 30 of which a lever contact end 32 and a switch contact end 33 are extended from both sides of a hinge axis 21 so as to oppose each other with respect to the hinge axis 21 on a proper position of the bracket 20. A micro switch 40 is installed within a turning radius of the switch contact end 33 of the actuator 30 on the bracket 20. One end of an elastic body 50 is fixed in position at the lever contact end 32 of the actuator 30 and the other end is fixed in to the bracket 20, so that the elastic body 50 always pulls the lever contact end 32 upward with respect to the hinge axis 21.
The hinge axis 21 is formed on the bracket 20 and a hinge hole 31 is provided in the center of the actuator 30, so that the actuator 30 can be combined to the bracket 20. The actuator 30 is one piece such that the lever contact end 32 is extended from the hinge hole 31 toward one end of the actuator 30, and the switch contact end 33 is extended from the hinge hole 31 toward the other end. Thus, when the lever contact end 32 moves downward, the switch contact end 33 moves upward.
The micro switch 40, connected to a power supply unit of a main body of the printer, is contacted by the switch contact end 33 of the actuator 30. The micro switch 40 is fixed on a printed circuit board 41, and the printed circuit board 41 is fixed on the upper surface of the bracket 20 by a screw, etc.
A tension coil spring 50 is used as an elastic body, and both ends thereof are fixed to fixed parts 32a and 20a in the actuator 30 and the bracket 20, respectively. The tension coil spring 50 pulls the lever contact end 32 of the actuator 30 so as to be in an upward position.
Referring to FIG. 2, when completely closing a front cover 60 provided for opening and closing a printer, a lever 61 on an inner surface of the front cover 60 is provided so that when the cover 60 is closed the lever 61 is within a turning radius of the lever contact end 32.
As shown in FIG. 2, in a case where a developer unit 70 is not mounted in the printer, the lever contact end 32 of the actuator 30 is pulled upward by the tension coil spring 50, thereby separating the micro switch 40 from the switch contact end 33 by a constant distance. At this time, although the lever 61 of the front cover 60 is in a closed state (referred to as an A state in FIG. 2), the lever 61 cannot be positioned so as to interfere with the motion of the actuator 30. Thus, the micro switch 40 cannot be connected to the power supply unit of the printer, and the supply of power to the printer is in an ‘OFF’ state.
As shown in FIG. 3, when the developer unit 70 is mounted into the printer, an upper surface 71 of the developer unit 70 pushes a lower surface of the switch contact end 33 of the actuator 30 upward. When the developer unit 70 has been mounted completely, the switch contact end 33 of the actuator 30 is moved upward more than the position thereof shown in FIG. 2, but not in a position of contact with the micro switch 40. Simultaneously, the lever contact end 32 is moved downward, so that the lever 61 can interfere with the lever contact end 32 (referred to as an A state in FIG. 3), when closing the front cover 60. In this case, since the micro switch 40 is not connected to the power supply unit of the printer, the power supply of the printer is in an ‘OFF’ state.
Sequentially, as shown in FIG. 4, if the front cover 60 is closed after completely mounting the developer unit 70, the lever 61 of the front cover 60 pushes the lever contact end 32 of the actuator 30 downward, and simultaneously the switch contact end 33 moves upward so that the micro switch 40 is connected to the power supply unit of the printer. At this time, the switch contact end 33 is separated from the upper surface 71 of the developer unit 70 and is supported by the end of the lever 61. In this case, since the micro switch 40 is connected to the power supply unit of the printer, the printer is turned ‘ON’, and the printer normally operates.
If the developer unit 70 is separated from the main body of the printer while replacing the developer unit 70 after opening front cover 60, the lever contact end 32 receives a tension force from the tension coil spring 50 as shown in FIG. 3 and FIG. 2. As a result, the power supply of the printer is automatically switched to an ‘OFF’ state.
In the devices for cutting off the power supply of the printer according to the related art, since the conventional devices have a large number of elements, the size of the devices are necessarily large, thereby increasing the size of the printer. Consequentially, it is difficult to obtain a compact and small printer. In addition, with an increase in number of elements, the probability of malfunction increases.
As described above, the structure of the device for cutting off the power supply of the printer according to the prior art is complicated. Also, since the actuator must operate both when the developer unit is replaced and when the front cover is manipulated, problems may be generated in actuator operation.